Coating and laminating process

ABSTRACT

A PROCESS FOR PREPARING A SELF-SUPPORTING LAMINATE HAVING A LOW PERMEABILITY TO GASES, COMPRISING APPLYING A COATING OF A FILM-FORMING POLYMER-DILUENT SYSTEM TO A SUBSTRATE; ADJUSTING THE THICKNESS OF THE COATING; DRYING THE COATING TO A SOLID STATE; APPLYING A COATING OF A DISPERSION OF A MINERAL INORGANIC, OR ORGANIC FILLER HAVING A PLATELIKE STRUCTURE TO THE RESULTING FILM; ADJUSTING THE THICKNESS OF THE COATING OF FILLER; APPLYING AT LEAST ONE COATING OR THE FILM-FORMING POLYMER-DILUENT SYSTEM TO THE   DRIED COATING OF FILLER; ADJUSTING THE THICKNESS OF THE COATING OF FILM-FORMING DILUENT SYSTEM; AND DRYING THE COATING OF FILM-FORMING DILUENT SYSTEM.

y 4, 1971 c.w. DESAULNIERS 3,577,508

COATING AND LAMINATING PROCESS Original Filed Oct. 17. 1966 FIG. I

FILLED POLYMER FILM suasmarg F IG. 3

POLYMER FILM FILLED POLYMER FILM FIG. 2

POLYMER FILM FILLED POLYMER FILM F /6. 5 suasrm r5 POLYMER FILM FILLERPOLYMER FILM Fla-4 POLYMER F ILM F IL L ER POLYMER FILM suasrmrs 7POLYMER FILM FILLED POL YMER FILM POLYMER FILM FIG. 6

90L YMER FILM FILLED POLYMER FILM I POLYMER FILM Charles W Desau/n/ersSUBSTRATE INVENTOR United States Patent 6 3,577,508 COATING ANDLAMINATING PROCESS CharlesW. Desaulniers, Franklin, Mass, assiguor to W.R. Grace & Co., New York, N.Y.

Original application Oct. 17, 1966, Ser. No. 587,194, new Patent No.3,499,820, dated Mar. 10, 1970. Divided and this application July 15,1969, Ser. No. 869,414

Int. Cl. B3212 19/02; B44d 1/14 U.S. Cl. 264--331 Claims ABSTRACT OF THEDISCLOSURE A process for preparing a self-supporting laminate having alow permeability to gases, comprising applying a coating of afilm-forming polymer-diluent system to a substrate; adjusting thethickness of the coating; drying the coating to a solid state; applyinga coating of a dispersion of a mineral, inorganic, or organic fillerhaving a platelike structure to the resulting film; adjusting thethickness of the coating of filler; applying at least one coating or thefilm-forming polymer-diluent system to the dried coating of filler;adjusting the thickness of the coating of film-forming diluent system;and drying the coating of film-forming diluent system.

CROSS REFERENCE TO RELATED APPLICATION This is a divisional ofapplication Ser. No. 587,194, filed Oct. 17, 1966, now U.S. Pat. No.3,499,820.

This invention relates to a novel and useful coating and laminatingprocess' More particularly, it relates to a coating and laminatingprocess whereby a film having an exceptionally low permeability to gasesincluding oxygen, nitrogen, water vapor, carbon dioxide, and the like isprepared.

It is an object of this invention to prepare a self-supporting laminate(see FIG. 1) having a low permeability to gases by a process comprisingapplying at least one coating of a filled film-forming polymer-diluentsystem selected from the group consisting of dispersions and solutionsto a substrate, and, after applying each such coating, adjusting thethickness of the coating, and drying the coating to a solid state,whereby a film is formed, the film being laminated to the substrate. Thesubstrate and film can be separated to yield a self-supporting filmhaving a loW permeability to gases.

It is an object of this invention to prepare a self-supporting laminate(see FIG. 2) having a low permeability to gases by a process comprisingapplying at least one coating of a filled film-forming polymer-diluentsystem selected from the group consisting of dispersions and solutionsto a substrate, and, after applying each such coating, adjusting thethickness of the coating, drying the coating to a solid state, whereby afilm is formed, the film being laminated to the substrate, applying atleast one coating of a film-forming polymer-diluent system selected fromthe group consisting of dispersions and solutions to the aforesaid film,and, after applying each such coating, adjusting the thickness of saidcoating of film-forming polymer-diluent system, and drying said coatingof filmforming polymer-diluent system to the solid state, whereby asecond film is formed, said second film being laminated to the filmprepared from the aforesaid filled filmforming polymer-diluent system.The substrate and film can be separated to yield a self-supportinglaminate film (see FIG. 3) having a low permeability to gases.

It is an object of this invention to prepare a self-supporting laminate(see FIG. 4) having a low permeability to gases by a process comprisingapplying at least one coating of a film-forming polymer-diluent systemselected from the group consisting of dispersions and solutions to asubstrate, and, after applying each such coating, adjusting thethickness of the coating, drying the coating to a solid state, whereby afilm is formed, said film being laminated to the substrate, applying acoating of a dispersion of filler to the film, adjusting the thicknessof the coating of filler, drying the coating of filler to asubstantially liquid free state, whereby a layer of filler is formed onthe first film, said layer of filler being on top of and laminated tothe film, applying at least one coating of the film-formingpolymer-diluent system selected from the group consisting of dispersionsand solutions to said layer of filler, and, after applying each suchcoating, adjusting the thickness of said coating, and drying saidcoating to the solid state, whereby a film is formed, said second filmbeing on top of and bonded to the layer of filler. The substrate andfilm can be separated to yield a self-supporting laminate film (see FIG.5) having a low permeability to gases. It is also an object of thisinvention to increase the flexibility of the layer of filler bypreparing it from a dispersion containing about (15-15%, based on thedry weight of the filler present, of a polymeric additive selected fromthe group consisting of polyvinyl methyl ether and polyethylene oxide.

It is an object of this invention to prepare a self-supporting laminate(see FIG. 4) having a low permeability to gases by a process comprisingapplying at least one coating of a film-forming polymer-diluent systemselected from the group consisting of dispersions and solutions to asubstrate, and, after applying each such coating, adjusting thethickness of the coating, drying the coating to a solid state, whereby afilm is formed, said film being laminated to the substrate, applying acoating of a dispersion of a purified clay-like mineral having aplatelike structure as defined infra to the film, adjusting thethickness of the coating of clay-like mineral, drying the coating ofclay-like mineral to a substantially liquid free state, whereby a layerof clay-like mineral is formed on top of said film, said layer beinglaminated to said film, applying a coating of a solution of at least onesalt of at least one element selected from the group consisting ofaluminum and the transition elements to said layer of clay-like mineral,allowing the coating of said solution to remain in contact with themineral layer for about 5 seconds to about 10 minutes, thereby to modifysaid mineral layer, washing said solution from the modified minerallayer, drying the modified mineral layer to a substantially liquid freestate, applying at least one coating of said filmforming polymer-diluentsystem to the thus washed and dried modified mineral layer, and afterapplying each such coating, adjusting the thickness of said coating, anddrying said coating to a solid state, whereby a film is formed, saidfilm being on top of and laminated to the layer of modified clay-likemineral. The substrate and film can be separated to yield aself-supporting laminate film (see FIG. 5) having a low permeability togases. It is also an object of this invention to increase theflexibility of the layer of filler by preparing it from a dispersioncontaining about 05-15%, based on the dry Weight of filler present, of apolymeric additive selected from the group consisting of polyvinylmethyl ether, polyethylene oxide, and the like.

It is an object of this invention to prepare a self-supporting laminate(see FIG. 6) having a low permeability to gases comprising applying atleast one coating of a film-forming polymer-diluent system selected fromthe group consisting of dispersions and solutions to a substrate, andafter applying each such coating, adjusting the thickness of thecoating, drying the coating to a solid state, whereby film of polymer isformed, said film being laminated to the substrate, applying at leastone coating of a filled film-forming polymer-diluent system consistingof dispersions and solutions to said first film, and, after applyingeach such coating, adjusting the thickness of the coating of filledpolymer-diluent system, drying the coating of filled polymer-diluentsystem to the solid state, whereby a film of filled polymer is formed,said film being on top of an laminated to the aforesaid film of polymer,applying at least one coating of a film-forming polymer-diluent systemselected from the group consisting of dispersions and solutions to thefilm of filled polymer, and, after applying each such coating, adjustingthe thickness of the coating of film-forming polymer-diluent system, anddrying the coating of polymer-diluent system to a solid state, whereby afilm of polymer is formed, said film being on top of and laminated tothe film of filled polymer. The substrate and film can be separated toyield a self-supporting laminate film (see FIG. 7) having a lowpermeability to gases.

It is an object of this invention to provide a process for coatingvarious substrates with a polymer film composition having a lowpermeability to gases such as oxygen, air, nitrogen, carbon dioxide,water vapor and the like. It is an object of this invention to provide aprocess for forming a laminate in situ from a film-forming plymer-diluent system selected from the group consisting of solutions anddispersions (including emulsions, suspensions, and latexes) offilm-forming polymers. It is an object of this invention to preparepolymer films having greatly reduced permeability to gases such as air,oxygen, nitrogen, water vapor, carbon dioxide, and the like frompolymer-diluent systems including latexes. It is another object of thisinvention to prepare a transparent glassclear laminated film frompolymer-diluent systems. It is another object of this invention toprepare films for use in packaging foods and other materials whichshould (or must) be protected from contact with the atmosphere. It isstill another object of this invention to prepare glassclear transparentlaminate films from polymer-diluent sys terns prepared from film-formingpolymers, whereby the resulting films have extremely low permeability togases including oxygen, air, water vapor, carbon dioxide, and the like.

Substrates with which I have used with excellent results in the processof this invention include glass surfaces, metal surfaces including anendless metal belt, wooden surfaces, aluminum foil, tin foil, plasticfilms and sheetsincluding films made of cellulose acetate, cellulosepropionate, cellulose butyrate, polyamides, polycarbonates, polyesters,polyethylene, corona treated polyethylenes, polypropylene, andpolystyreneother suitable substrates including paper, paperboard,wallboard, cloth, canvas, wood, and the like.

This invention is also directed to an article of manufacture comprisingan self-supporting laminate having a low permeability to gases, saidlaminate having a film of filled polymer, and a film of polymer bondedto the film of filled polymer (see FIG. 3); said article can be bondedto a substrate (see FIG. 2).

This invention is also directed to an article of manufacture comprisinga self-supporting laminate having a low permeability to gases, saidlaminate having a first film of polymer, a film of filler bonded to thefirst film of polymer, and a second film of polymer bonded to the filmof filler (see FIG. 5); said article can be bonded to substrate (seeFIG. 4).

This invention is also directed to an article of manufacture comprisinga self-supporting laminate having a low permeability to gases, saidlaminate having a substrate, and a film of filled polymer bonded to thesubstrate (see FIG. 1).

This invention is also directed to an article of manufacture comprisinga self-supporting film of filled polymer, said film having a lowpermeability to gases.

This invention is also directed to an article of manufacture comprisinga self-supporting laminate having a low permeability to gases, saidlaminate having a first film 4 of polymer, a film of filled polymerbonded to the first film, and a second film of polymer bonded to thefilm of filled polymer (see FIG. 7); said article can be bonded to asubstrate (see FIG. 6).

This invention is also directed to an article of manufacture comprisinga self-supporting laminate film having a low permeability to gases, saidlaminate having a first film of polymer, a film of filler bonded to thefirst film of polymer and a second film of polymer bonded to the film offiller in which the filler contains about 05-15% (preferably 14% basedon the dry weight of the filler, of a polymeric additive selected fromthe group consisting of polyvinyl methyl ether, polyethylene oxide, andthe like, to increase the flexibility of the laminate (see FIG. 5 saidarticle can be bonded to a substrate (see FIG. 4).

In the drawing:

The drawing illustrates the laminates of this invention.

In one embodiment of my invention I strip a film which was formed by myprocess from the surface (e.g., polished glass surface, polished metalsurface, or substrate, such as a rotating drum or endless belt, or thelike) on which the film was prepared, thereby to obtain a substantiallyclear transparent film which is substantially impervious to gasesincluding oxygen, nitrogen, air, water vapor, carbon dioxide, and thelike. In another embodiment of my invention, I leave the film on thesubstrate, or surface, or base, or support, on which it was formed(e.g., a base which can be another plastic film-cg, polyethylene, coronatreated polyethylene, polypropylene, other polyolefins, and thelikewood, paperboard, metal foil, paper, cloth, or the like), thereby toform a laminate comprising the thus formed film bonded to the base orsubstrate on which said film was formed.

In one embodiment of this invention I coat, or precoat, the substratewith a primer, to faciliate bonding between the substrate and the filmformed thereon, before applying a coating of a polymer-diluent system tosaid substrate. Hercoprime (an atactic polypropylene in an aromaticsolvent) is a preferred primer. Other primers will be readily apparentto those skilled in the art.

My invention fills a long standing need and is entirely unobvious andcompletely unexpected. Packaging films in general exhibit substantialpermeability to oxygen and other gases, including water vapor, presentin the atmosphere. For example, the permeability of polyethylene film tooxygen is about 1.04 10 cc. (s.t.p.) cm./cm sec. atm. at 35 C. while thepermeability film comprising a copolymer of vinylidene chloride andacrylonitrile to oxygen was found to be about l.8 l0- cc. (s.t.p.)cm./cm. sec. atm. at 35 C.

I have found that substantially any substance-mineral, inorganic, ororganic-existing in the form of platelets or particles having aplatelike structure (i.e., existing in the form of platelets having anaxial ratio of about 20300:1 and a maximum length of about 20-30microns), being substantially insoluble in the polymer-diluent system towhich it is added or brought into contact in the process of thisinvention and being substantially resistant to the hydrating anddisintegrating action of waterincluding water vapor-can be used withexcellent results as a filler in the process of my invention. By theterm filler, I mean at least one substance having a platelike structureselected from the group consisting of mineral, inorganic, and organicmaterials which, where incorporated into a polymer-diluent systemcomprising solutions and dispersions (including emulsions and latexes)of film-forming polymers render films made therefrom substantiallynonpermeable to gases such as oxygen, nitrogen, air, water vapor, carbondioxide, and the like; said substance, where mineral, can be a naturallyoccurring mineral, a synthetic mineral, or a chemically modifiedmineral. By the term filler I also mean at least one substance selectedfrom the aforesaid materials which, where present as a layer laminated,or bonded, between at least two layers of film formed from suchpolymer-diluent systems, renders such laminate substantiallynonpermeable to gases including those listed supra.

By the term filled film-forming polymer-diluent system, I mean apolymer-diluent system to which about 5- 95% (based on the total weightof the system), of filler as defined supra, has been added. Examples ofsuch substances (fillers) include graphite platelets, platelets ofmetals such as aluminum, platelets of alloys such as bronze, and organicsubstances having a platelike structure and being substantiallyinsoluble in the polymer-diluent system (e.g., N-benzoyl acetamide Wherewater is the diluent), and the like. Numerous other examples ofinorganic and organic substances suitable for use in the process of thisinvention will be readily apparent to those skilled in the art. I havealso found that minerals having the above-defined platelike structure(e.g., platy clays, mica, vermiculite, platy talc, and the like) aregenerally too susceptible to the hydrating and disintegrating action ofWater vapor present in the atmosphere to be satisfactory for use in theprocess of my invention. I have found that films prepared from suchminerals have very low permeability to substantially dry gases. However,if such films are exposed to air having a high moisture content, such asis frequently encountered in the Mississippi Valley during the summer,the moisture present in such air permeates the films and substantiallyincreases the air and oxygen permeability thereof. I have made theunobvious and completely unexpected discovery that this susceptibilityto moisture can be eliminated by modifying such minerals (i.e., bytreating them with ions selected from at least one member of the groupconsisting of aluminum (III) and positive ions of transition elements).By transition elements, I mean elements having atomic numbers 21-32,3951, and 57-83. I generally prefer to modify such minerals by treatingthem with iron (III), chrominum (III), and Zirconium (IV) ions. I haveobtained optimum results with chromium (III) and zirconium (IV) ions.

I have found that there are three general methods by which the laminatesof my invention can be prepared, these are:

FIRST GENERAL METHOD To a polymer-diluent system prepared from afilmforming polymer and having a solid content of about 5- 70%, I add afiller, which is insoluble in the polymerdiluent system, in suchquantity as to form a polymer-diluent-filler system comprising about595% filler. Said filler has a platelet or platelike shape and an axialratio (length to thickness) of about 20300:1 and a maximum length up toabout 20-30 microns. I have obtained excellent results with suchparticles, e.g., 0.005-5 microns; I have also obtained optimum resultswith particles having a length of about 0.01-1 micron. Fillers having aplatelike structure and which I have found to give excellent results inthe process of my invention include vermiculite, mica, talc having aplatelet or platelike structure (that having a fibrous structure isunsatisfactory), graphite, clays having a platelike structure (e.g.,bentonite), aluminum platelets, bronze platelets, and platelets of waterinsoluble organic compounds such as N-benzoyl acetamide, and similarmaterials. However, Where using clay-like minerals (i.e., vermiculite,mica, talc, clays, and the like having a platelike structure) as fillersfor laminates, including laminate films, I have found that thepermeability to humid, or moist, air of such laminates can be greatlydecreased by modifying said fillers. As used herein the term modifyingclay-like minerals means to treat said minerals with at least one saltof at least one element selected from the group consisting of aluminumand the transition elements, whereby the permeability to humid air oflaminates filled with the thus treated minerals is substantially lessthan that of similar laminates filled with the same minerals which havenot been treated with at least one salt of aluminum or a transitionelement. The term modified clay-like fillers means clay-like minerals 6which have been subjected to the above-mentioned modifying treatment.

Since commercially available clay-like minerals contain impurities (suchas silica, particles of rock, and some very large particles of clay-likeminerals), I have found that such minerals should be refined beforeusing them in the process of my invention. Although many ways toaccomplish such refining will be readily apparent to those skilled inthe art, I prefer to do this by forming a suspension of about 0.110% ofthe clay-like mineral (preferably about 2%) in Water, agitating theresulting mixture vigorously, and adding a small amount (0.1-5 based onthe weight of the clay-like mineral present) of a dispersing andexfoliating agent such as sodium polyphosphate, sodium hydroxide, sodiumcarbonate, sodium oxalate, sodium phosphate, or the like to theresulting slurry, thereby to disperse and exfoliate the claylikemineral. After thorough mixing I separate, for example by centrifugingor by decanting, the resulting dispersion (or slurry) from the fewremaining large particles (including a small quantity of mineral whichwas not exfoliated).

The dispersion is now ready for treatment with a solution of at leastone salt of aluminum or a transition element, whereby the properties ofthe filler (especially its resistance to water vapor) are improved. Iprefer to conduct such treatment by adding to the dispersion ofclay-like mineral a solution of at least one salt of at least oneelement selected from the group consisting of aluminum and thetransition elements, in which said element is present as a cation, whilestirring the dispersion as the solution of said salt is added slowlythereto. The dispersion will take on a more and more fiocculatedcharacter as the solution of said salt is added until fiocculation issubstantially complete. I then separate the clay-like mineral by aconventional method such as decantation, filtration, or centrifugation,and I wash the thus separated clay-like material to remove any salts andother impurities which are present in the mother liquor or adhering tothe clay-like mineral.

In another embodiment of this invention I treat the clay-like mineralwith at least one ion selected from the group consisting of ions ofaluminum and the transition elements by passing a dispersion, or slurry,of said mineral through an ion exchange column which has been preparedby passing a concentrated aqueous solution of at least one salt of atleast one element selected from the group consisting of aluminum and thetransition elements in which the aluminum or transition element ispresent as a cation through a column packed with a conventional hydrogenform of an ion exchange resin. For example, a solution of chromiumchloride can be passed through a column containing a conventional ionexchange resin in the hydrogen form, thereby to convert said resin fromthe hydrogen form to the chromium form. The dispersion of clay-likemineral is then passed through the ion exchange resin, and the thustreated clay-like'mineral is recovered and washed. I have found thatpassing the dispersion of clay-like mineral through a resin bed at arate of about 0.0050.3 bed volume per minute gives excellent results. Ithen separate and Wash the resulting modified clay-like mineral andredisperse the thus *washed modified clay-like mineral to make a slurrysuitable for use as a filler in the process of my invention. Where usinggraphite, aluminum platelets, bronze platelets, or similar metalplatelets, and platelike organic materials it is not necessary to treatsaid graphite, or metal, or organic platelets with a compound ofaluminum or a transition element. Where using such materials, I make adispersion, or suspension, or slurry of the platelets by adding saidplatelets to water, agitating the mixture and then separating, bydecantation or centrifugation, any large patricles which might bepresent. The resulting slurry is then ready for use in the process of myinvention.

Where using a modified clay-like mineral as filler in a polymer-diluentsystem where the addition of water will not produce harmful results(e.g., the coagulation or precipitation of the polymer, the formation oftwo liquid phases, or the excessive dilution of the resultingpolymer-diluent-filler system), an aqueous dispersion (containing about0.58% solids, preferably about 25% solids) of the modified mineral inwater can be added to a film-forming polymer-diluent system. Where waterwould be harmful, the modified clay-like mineral is recovered from thedispersion in which it was prepared and dried. The thus dried modifiedclay-like mineral filler is then added to the polymer-diluent system toyield a polymer-diluent-filler system.

As stated supra, I use a polymer-diluent system containing about 570%solids. To this I add sufficient filler having a platelike structure, orshape, to produce a polymcr-diluent-filler system in which the fillerconstitutes 595% of the weight of said polymer-diluent-filler system.

I prepare a laminate by applying at least one coating of thefilm-forming polymer-diluent-filler system to a substrate or surface anddraw the wet (i.e., diluentcontaining) coating to the desired thicknesswith conventional apparatus (e.g., a Meyer Bar, Baker Film ApplicatorBar, doctor bar, or the like) in a conventional manner. I prefer to draweach wet coating to such thickness that on drying it will yield a filmof filled polymer (bonded to the substrate) about 0.5-3 mils thick (1mil is 0.001 inch). I then dry said first coating at such a temperaturethat the moisture (i.e., diluent) will be evaporated from the film butthat the polymer will not be burned, charred, or otherwise decomposed byheat, thereby to form a laminate which is substantially nonpermeable togases such as air, oxygen, nitrogen, water vapor, carbon dioxide, andthe like, said laminate comprising a film of filled polymer laminated,or bonded, to said substrate, or surface. Said film can, if desired, bestripped from said surface if said surface is a smooth surface such aspolished glass, smooth metal, and the like.

The drying temperature will obviously depend upon the type of polymerfrom which the polymer-diluent system was made, upon the boiling pointand vapor pressure of the diluent, and upon the residence time in thedrying oven (or drying or heating Zone). I have found that temperaturesranging from about 100 to about 140 C. have given excellent results;however, temperatures considerably lower than this and temperatures agreat deal higherparticularly where using short residence time in theheating zonehave also been used with excellent results. In someinstances, e.g., to fill pinholes formed in the filled polymer filmbonded to the substrate, I add a second coating of the aforesaidpolymer-diluent-filler. I draw the second coating down and dry itaccording to the procedure used with the first coating. I usually makethe second film about the same thickness as the first; however, it canbe thinner or thicker as choice dictates. I can, if desired, addadditional, i.e., a third, fourth, fifth, etc. coatingafter drawing downand drying each underlaying coating. I can, if desired, strip the thusformed film from the substrate, or support on which it was formed andrecover a laminate film comprising the aforesaid first film and theaforesaid second film laminated, or bonded, together. Alternatively, Ican leave the resulting film laminated to the substrateespecially wherethe substrate is paper, paperboard, cloth, wood, or plastic film.

SECOND GENERAL METHOD In another embodiment of my invention I do not addfiller having a plate-like structure to the film-forming polymer-diluentsystem. Instead, I modify the general procedure described supra by usinga polymer-diluent system to which no filler has been added. Saidpolymerdiluent system is of the type described supra and has a polymercontent of about 5-70%. I coat a substrate (e.g., a substrate of thetype mentioned supra) with the polymerdiluent system and draw theresulting wet coating to a thickness which will yield a first polymerfilm, or first polymer layer, of about 0.053 mil dry thickness, and drysaid wet coating. In some instances after drying this coating I preferto apply a second coating, or layer, of the polymer-diluent system ontop of the thus prepared first dry film, or dry layer. The resultingsecond layer, or second film, can have a dry thickness about the sameas, or thicker, or thinner than that of the first layer. After dryingthe first layer (or the second or subsequent, i.e., third, fourth, etc.,layer where a second or subsequent layer is used) I coat the thus driedfilm with a dispersion of filler (e.g., modified clay-like mineral,graphite, or metal platelets, or platelets of an organic material, saidfiller being substantially insoluble in the polymer-diluent system).(Where only one layer of the polymer-diluent system is used, I coat saidlayer with said dispersion of filler.) Said filler is dispersed in amedium in which the filler and the polymer are substantially insoluble.I prefer to draw the coating of said filler down to such wet thicknessthat where dry it will have a thickness of about ODDS-0.2 mil. I thendry this wet coating, or film, under such conditions that will render itsubstantially dry but under conditions of temperature that will not burnor otherwise damage the polymer or the filler. I have found thattemperatures of about to about C. give excellent results; however, Ihave also obtained excellent results with higher and lower temperaturesdepending upon the residence time of the film in the heated zone and onthe vapor pressure of the medium being evaporated. Subsequently, I applya coating of the polymerdiluent system and draw it to such thicknessthat it will yield a film having a dry thickness of 005-3 mil on top ofthe thus dried coating of filler. I dry this coating until it issubstantially free of diluent but under such conditions that neither thepolymer nor the filler is burned, charred, or otherwise damaged by thedrying process. In some instances, I prefer to put a second coating, orlayer, of the polymer-diluent system upon the coating, or layer, which Ihave previously applied and dried on top of the coating of plate-likefiller. Where applying such additional coating of polymer-diluentsystem, said coating may be the same thickness as the previous coatingor it may be thicker or thinner. If desired, a third, fourth, fifth,etc. coating of the polymer-diluent system can be applied and drawn downand dried in the usual manner.

THIRD GENERAL METHOD In still another embodiment of my invention Iprefer to use the general method outlined in the Second General Method,supra, except that I use a slurry of clay-like mineral which has notbeen modified by treating with a salt of aluminum or at least oneelement of the transition group. Where using this procedure one or twocoatings of the polymer-diluent system are applied, drawn down, anddried as before and a coating of a suspension of clay-like mineral whichhas not been modified by treatment with a salt of aluminum or atransition group element is applied on top of the thus prepared polymerfilm; said coating is drawn down to produce a film which will have a drythickness of about 0.0050.2 mil. This material is then dried and treatedwith a solution of a salt of aluminum or a transition element, washedwith water, dried, and coated with one or two layers of polymer filmusing the general procedure outlined where discussing the Second GeneralMethod, supra.

Diluents which I have found to be especially useful in the process of myinvention include: water, tetrahydrofuran, carbon tetrachloride,ethylene dichloride, methanol, ethanol, isopropyl alcohol, toluene,xylene, acetonitrile, hexane, heptane, dimethyl formamide, and dimethylsulfoxide. Other diluents will, on the basis of the disclosures 9presented in this patent application, be readily apparent to thoseskilled in the art.

Film-forming polymers with which I have obtained excellent resultsinclude homopolymers of vinyl chloride, copolymers of vinylidenechlorides with monomers selected from the group consisting of methylacrylate, ethyl acrylate, acrylamide, and acrylonitrile, homopolymers ofvinyl acetate and copolymers of vinyl acetate with monomers selectedfrom the group consisting of methyl acrylate, ethyl acrylate,acrylamide, and acrylonitrile. I have also obtained excellent resultsusing copolymers in which polyvinyl chloride was the principalconstituent. Where using copolymers of vinylidene chloride, I prefer touse those in which polyvinylidene chloride constitutes the majorcomponent; however, I have obtained excellent results with copolymers ofvinylidene chloride in which the vinylidene chloride is not the majorcomponent. Where using the copolymers of vinyl acetate, I prefer to usethose in which polyvinyl acetate is the major component; however, I haveobtained excellent results with such copolymers in which the polyvinylacetate was not a major component.

Numerous other polymers and copolymers which will give excellent resultsin the process of my invention will, as a consequence of the disclosurescontained herein, be readily apparent to those skilled in the art.

I have obtained excellent results where using aqueous dispersions offilm-forming polymers, i.e., film-forming latexes, in the process of myinvention. Excellent results have been obtained with such latexes inwhich the polymer particles have diameters ranging from about 200 A.(Angstrom units) to about 100,000 A.; however, I prefer to use polymerparticles ranging in diameter from about 700 A. to about 4,500 A.

As a consequence of the disclosures presented herein, numerousmodifications of the procedures and embodiments of my invention will bereadily apparent to those skilled in the art.

I prefer to measure the permeability of films to gases and vapors with adevice known as an Amicon Permeameter. Said device measures the rate ofchange of pressure in a previously evacuated space, of known volume,downstream of the film whose permeability is being measured. Said filmis positioned between two sections of a permeability cell; said cell isclosed and sealed by bolting two out flanges together. The sealed cellis attached to a vacuum line, attached to a vacuum pump, and evacuatedto a pressure of 1 10 mm. of mercury. After allowing sufficient time foroutgassing, oxygen, or other gas or vapor, is admitted at a pressure ofabout 500 mm. of mercury to the portion of the cell which is upstream ofsaid film. The portion of the cell which is downstream of the film isthen disconnected from the vacuum line; and the rate of change inpressure of said downstream portion of said cell is recorded using aconventional differential pressure sensor. Said pressure sensor recordspressure changes as low as 0.01 micron per minute. Permeability iscalculated from the slope of a curve obtained by plotting downstreampressure vs. time in minutes. Other procedures for measuring thepermeability of films will be readily apparent to those skilled in theart.

My invention will be further illustrated by the following examples whichare illustrative only and which are not intended to limit the scope ofthe invention.

EXAMPLE I A suspension of about 2% of bentonite clay in water at about60 C. was agitated with rapid stirring and treated with sodiumpolyphosphate as a dispersing and exfoliating agent. About 0.5% sodiumpolyphosphate, based on the weight of the clay present, was added. Whendispersion was substantially complete, after about 2 hours, stirring wasdiscontinued and a small amount of larger unexfoliated clay particlesand a few particles of rock, silica, and the like were allowed to settleout. The dispersion was decanted from the particles which had settled,thereby to obtain a dispersion of a purified clay-like materialpurifiedbentonite clay. A one molar solution of chromium (III) chloride wasslowly added to the suspension of purified clay while stirring saidsuspension. As the chromium salt was added, the clay fiocculated slowlyuntil flocculation of the clay was finally complete. The thusfiocculated clay was separated from the supernatant liquor and washedwith water, thereby to yield at modified clay suitable for use as afiller in the process of this invention. The thus washed modified claywas redispersed in an aqueous solution of sodium polyphosphate (about0.5% sodium polyphosphate, based on the weight of the modified clay) andenough water to form a dispersion containing about 8% of the modifiedclay. The resulting dispersion of modified bentonite clay was labeledDispersion No. 1.

A latex (i.e., an aqueous dispersion) of a copolymer of vinylidenechloride and vinyl chloride having a solid content of about 40% wasmixed with a sufiicient quantity of the above-mentioned Dispersion No. 1to produce a composition, or slurry, designated Composition A,containing about 15% of said modified clay and copolymer based on thesolid content of the resulting slurry, or composition. After mixing theslurry thoroughly, a quantity of it was applied as a first coating to asmooth glass surface and drawn down with a Baker Film Applicator. Thecoating was drawn to such thickness that, after drying at about 125 C.for about 3 minutes, a first layer of a filled polymer film having athickness of about 0.5 mil resulted. A second coating of the aforesaidComposition A, of substantially the same thickness as the aforesaidfirst coating, was applied to said first coating and dried using thesame application, drawing, and drying procedure that was used with saidfirst coating, thereby to fill pinholes in the first layer of polymerfilm and to produce a film having a total thickness of about 1 mil andconsisting of a film of modified clay filled polymer laminated, orbonded to a substrate (the glass surface). This film was stripped fromthe glass surface.

The permeability of the dried transparent film to oxygen was measuredand found to be less than 1X 10* cc. (s.t.p.) cm./cm. sec. atm. at 35C.; this contrasts with a value of about at 35 C. for a film preparedfrom the same latex but without the addition of the chromium modifiedclay filler.

EXAMPLE II The general procedure of Example I was repeated using theforesaid Composition A, but in this instance only one coating wasapplied to a glass surface, or substrate. Said coating was drawn, whilewet, to such thickness that after drying for about 4 minutes at C. ithad a thickness of about 0.8 mil, thereby forming a laminate comprisingsaid film laminated to the glass substrate. A ortion of said film wasstripped from the glass surface, and its (the films) permeability tooxygen was determined and found to be less than 1X 10- cc. (s.t.p.)cm./cm. sec. atm. at 35 C.

EXAMPLE III The general procedure of Example I was repeated, however, inthis instance the clay used was bentonite which had been treatedaccording to the general method of Example I except that zirconium (IV)chloride was used, i111 place of chromium (III) chloride, to treat thebentonite c ay The results obtained in this example were substantiallyidentical to those obtained in Example I.

EXAMPLE IV A first polymer film was prepared by applying a first coatingof a latex comprising a copolymer of vinylidene chloride andacrylonitrile having a solid content of about 55 on a smooth metalsurface using a Baker Film Applicator Bar to draw the wet film down.This coating was dried at about 120 C. for about minutes, therebyyielding a dry film, or layer, having a thickness of about 0.6 mil. Acoating, or layer, of the dispersion of modified clay prepared inExample I, supra (i.e., Dispersion No. 1), was then applied on top ofthe thus dried film, drawn down with a Baker Film Applicator Bar, anddried at about 120 C. for about 5 minutes. The resulting layer ofmodified clay had a thickness of about 0.05 mil. A second coating, orlayer, of the aforesaid latex was then applied on top of the dried claycoating, using the same procedure that was used where applying theaforesaid first coating, and dried at about 120 C. for about 5 minutes;the resulting dried laminate film had a total thickness of about 1.25mil. Said film was stripped from the support (substrate) on which it wasformed. The permeability of this laminate film to oxyen and humid airwas less than 1 l0 cc. (s.t.p.) cm./cm. sec. atm. at 35 C.

EXAMPLE V A first coating of a vinylidene chloride ethyl acrylatecopolymer latex having a solid content of about 55% was applied to apolished metal surface using a Baker Film Applicator Bar to draw thecoating down. The resulting wet film was dried at about 130 C. for about3 minutes; it yielded a dry first film having a thickness of about 0.5mil bonded to the metal surface.

A dispersion of bentonite clay filler was prepared by adding asufficient amount of said clay to give a dispersion, or slurry, of aboutsolid content to water, stirring the mixture, and adding theretosufiicient sodium hydroxide to bring the pH to about 89, thereby toexfoliate and suspend the clay. The mixture was stirred until dispersionwas substantially complete (ca. for about 1.5 hour). The dispersion wasthen separated (by centrifugation) from a small quantity of largeparticles, unexfoliated clay, silica, and the like, which had settled tothe bottom. The thus separated dispersion was labeled Dispersion No. 2.

A coating of Dispersion No. 2 was applied to the aforesaid first filmusing a Baker Film Applicator Bar to draw the wet coating down. The clayfilm was dried for about 3 minutes at about 130 C., thereby to give afilm, or layer, of said filler about 0.04 mil thick. Said clay film wastreated with an excess of a solution of about 0.1 molar chromium (III)sulfate for a period of about 10 minutes. The clay film swelled somewhatduring this treatment but it retained its integrity. The excess chromiumsalt solution was flushed, or washed, from the film with water and thefilm was dried for about 3 minutes at about 130 C., thereby yielding afilm of modified claylike material bonded to the aforesaid first film. Asecond coating of the aforesaid latex was applied to the thus driedehrominum-treated clay layer using a Baker Film Applicator Bar to drawthe wet coating down. Said second coating was dried at about 130 C. forabout 3 minutes, thereby yielding a film of latex having a thickness ofabout 0.5 mil on top of and bonded to the aforesaid clay layer. Theresulting laminate film was stripped from the metal surface, orsubstrate, upon which it was formed.

The permeability to oxygen of said laminate film was less than 1 10 cc.(s.t.p.) cm./crn. sec. atm. at 35 C.

EXAMPLE VI The general procedure of Example V was repeated, but in thisinstance the dried clay coating, or film, was treated with a nearlysaturated solution of zironium (IV) nitrate rather than with a solutionof chromium sulfate. The results obtained in this example wereSubstantially identical to those obtained in Example V.

12 EXAMPLE VII The general procedure of Example V was repeated, but inthis instance the dried clay coating, or film, was treated with a 0.5molar solution of iron (III) chloride rather than with a solution ofchromium sulfate. The results were substantially identical to thoseobtained in Example V.

EXAMPLE VIII A copolymer of vinylidene chloride and vinyl chloride wasdissolved in tetrahydrofuran to produce a solution containing about 10%of said copolymer. A first coating of this solution was applied to apaperboard surface, the wet coating was drawn down with a Baker FilmApplicator Bar and the solvent was evaporated; the resulting film wasdried for about 3 minutes at about C., thereby to yield a dry firstpolymer film having a thickness of about 0.4 mil laminated to asubstrate (the paperboard surface). A second coating of said solution ofcopolymer was applied in a similar fashion, the solvent was evaporated,and the film was dried as before. This resulted in the formation of afilm having a total thickness of about 0.7 mil laminated to thepaperboard surface. A slurry of chromium-treated bentonite filler,prepared by the general procedure of Example I, and containing about 3%solid was applied, as a coating, to the thus prepared polymer film. Thecoating of chromium-treated bentonite was drawn down and dried for about3 minutes at about 125 C., thereby to form a film, or layer, of modified(chromium-treated) bentonite filler of about 0.04 mil on the previouslyprepared polymer film surface. Said modified bentonite clay film, orlayer, was then overcoated with a coating (called the third coating) ofthe aforesaid polymer solution. Said coating of polymer solution wasapplied in the same fashion as the aforesaid first polymer coating. Thesolvent was evaporated, and the resulting third polymer film was driedfor about 3 minutes at about 125 C.; the third film, or layer, ofcopolymer was overcoated with a fourth coating of the polymer solutionin the same fashion that the aforesaid first polymer film was overcoatedwith the aforesaid second coating of polymer solution. The solvent wasevaporated from the fourth polymer coating and the resulting film wasdried at about 125 C. for about 3 minutes. The resulting laminatecomprised a paperboard substrate laminated to a primary film of polymer,a film of filler (modified bentonite) laminated to the primary film ofpolymer, and a secondary film of polymer laminated to the film offiller. The primary and secondary films of polymer were each about 0.35mil thick and the film of filler was about 0.04 mil thick. The resultingstructure was substantially nonpermeable to gases includingmoisture-laden oxygen and humid air.

EXAMPLE IX The general procedure of Example VIII was repeated, however,in this instance a copolymer of vinylidene chloride and vinyl chloridewas dissolved in dioxane. The results were substantially identical tothose obtained in Example VIII.

EXAMPLE X The general procedure of Example VIII was repeated; however inthis instance the polymer used was a copolymer of vinylidene chlorideand ethyl acrylate. The polymer was dissolved in tetrahydrofuran toproduce a solution containing 10% of polymer. The results obtained weresubstantially identical to those obtained in Example VIII.

EXAMPLE XI The general procedure of Example X was repeated; however, inthis instance a sheet of polyester film (ca. 1 mil thick) was used inplace of the paperboard as backing for the laminate. The polyester filmwas coated with a thin layer (ca. 0.01 mil, dry thickness) or Hercoprime(an atactic polypropylene in an aromatic solvent) and the solvent wasevaporated before applying the vinylidene chloride ethyl acrylatepolymer solution. The resulting laminate was substantially nonpermeableto air and oxygen, including moisture-laden air and moisture-ladenoxygen.

EXAMPLE XII The general procedure of Example VIII was repeated. However,in this instance the substrate, or surface, on which the polymersolution was coated was a polished glass surface, and the layer, orfilm, or chromium treated bentonite clay was replaced by a layer, orfilm, consisting of platelets, or platelike particles, of aluminum. Thelayer of aluminum platelets was applied by forming an aque ousdispersion of about 2% of aluminum platelets in water, coating thepreviously formed dry polymer film, or layer, with said aqueousdispersion, drawing the resulting coating of aluminum filler down with aBaker Film Applicator Bar, and drying the thus drawn coating to form afilm, or layer, of aluminum platelets about 0.03 mil thick. The thusformed film of aluminum platelets was then overcoated with two coatingsof polymer solution using the general procedure of Example VIII.

The resulting laminate comprising a layer, or film, of aluminumplatelets laminated, or bonded, between two layers, or films, of polymerwas stripped from the glass surface. Said film was found to have apermeability to oxygen of less than A dispersion of about 10% ofplatelets, or platelike particles, of N-benzoyl acetamide was preparedby adding said particles of N-benzoyl acetamide to water. The mixturewas stirred vigorously for about 15 minutes, allowed to stand for about5 minutes, and the resulting dispersion of suspended particles wasdecanted from a few large particles which had settled out. The thusobtained dispersion was labeled Dispersion VIII.

A latex of a copolymer of vinylidene chloride and vinyl chloride havinga solid contentof about 40% was mixed with a sufficient quantity of theabove-described Dispersion XIII to produce a composition, or slurry,containing about 12% N-benzoyl acetamide and 88% copolymer based on thesolid content of said composition.

After thoroughly mixing the above-described composi tion, a quantity ofit was applied as a first coating to a smooth glass surface. Saidcoating was drawn down, with a Baker Film Applicator Bar, to suchthickness that, upon drying for about 4 minutes at about 110 C. itformed a film having a thickness of about 0.4 mil. A second coating ofthe aforesaid composition was applied to the aforesaid film using thesame application, drawing, and drying procedure that was used with saidfirst coating, thereby to produce a filled film having a thickness ofabout 0.8 mil laminated, or bonded, to the glass surface.

The film was stripped from the glass surface and tested for permeabilityto oxygen. Its permeability to oxygen was found to be less than 1X cc.(s.t.p.) cm./cm. sec. X atm. at 35 C.

EXAMPLE XIV The general procedure of Example XIII was repeated; however,in this instance the dispersion of platelets of N- benzoyl acetamide wasreplaced with about a 9% dispersion of graphite platelets in water. Theresults were substantially identical to those obtained in Example VIII.

EXAMPLE XV The general procedure of Example IV was repeated. However, inthis instance a portion of Dispersion No. 1 was modified by addingthereto about 2%, based on the dry weight of the modified clay filler insaid Dispersion No. l, of polyvinyl methyl ether thereby to yield amodified dispersion (Dispersion No. 1-A). Dispersion No. 1-A wassubstituted, in the instant example, for the Dis- 14 persion No. 1 usedin Example IV. The resulting laminate film was stripped from the metalsurface (substrate). The permeability of this film to moist oxygen andhumid air was less than 1X 10* cc. (s.t.p.) Xcm./cm. sec. Xatm. at 35 C.

It was found that incorporation of the polyvinyl methyl ether into thedispersion of modified clay from which the layer, or film, of filler wasprepared rendered the laminate film of this example more flexible thanthe laminate film of Example IV. That is, bending the film preparedaccording to this example 180 around a /2-inch mandrel and flexing saidfilm 10 times did not increase the permeability of said film to moistoxygen. Au identical bending and flexing treatment greatly increased tomoist oxygen permeability of the laminate film of Example IV.

EXAMPLE XVI The general procedure of Example XV was repeated. However,in this instance the polyvinyl methyl ether of Example XV was replacedwith about 2%, based on the dry weight of modified clay filler inDispersion No. 1, of polyethylene oxide. The results obtained with thelaminate film of the instant example were substantially identical tothose obtained with the laminate film of Example XV. In other words,incorporation of polyethylene oxide into the modified clay fillerrendered the laminate film of this example more flexible than thelaminate film of Example IV.

EXAMPLE XVII A suspension of about 2% bentonite clay in water at about60 C. was agitated with rapid stirring and treated with sodiumpolyphosphate as a dispersing and exfoliating agent. About 0.5% sodiumpolyphosphate, based on the weight of the clay present, was added. Whendispersion was substantially complete, after about 2 hours, stirring wasdiscontinued and a small amount of larger unexfoliated clay particlesand a few particles of rock, silica, and the like were allowed to settleout. The dispersion was decanted from the particles which had settled,thereby to obtain a dispersion of a purified clay-like materialpurifiedbentonite clay. The purified bentonite clay was recovered from thedispersion by centrifugation and redispersed in water to give adispersion containing about 8% of said clay; this dispersion wasdesignated Dispersion 8.

A latex (i.e., an aqueous dispersion) of a copolymer of vinylidenechloride and vinyl chloride having a solid content of about 40% wasmixed with a suflicient quantity of the above-mentioned Dispersion 8 toproduce a composition, or slurry, containing about 15% of said purifiedbentonite clay and copolymer based on the solid content of the resultingslurry, or composition. After mixing the composition thoroughly, aquantity of it was applied as a first coating to a smooth glass surfaceand drawn down with a Baker Film Applicator. The coating was drawn tosuch thickness that, after drying at about C. for about 3 minutes, afirst layer of a filled polymer film having a thickness of about 0.5 milresulted. A second coating of the aforesaid composition, ofsubstantially the same thickness as the first coating, was applied tosaid first coating and dried using the same application, drawing, anddrying procedure that was used with said first coating, thereby to fillpinholes in the first layer of polymer film and to produce a film havinga total thickness of about 1 mil and consisting of a film of clay filledpolymer laminated, or bonded to a substrate (the glass surface). Thisfilm was stripped from the glass surface.

The permeability of the dried transparent film to dry oxygen wasmeasured and found to be less than 1x10- cc. (s.t.p.) cm./cm. sec. atm.at 35 C. However, the permeability of said film to moist oxygen was onlyabout 1 10 cc. (s.t.p.) crn./cm. sec. atm. at 35 C.

The film prepared in the instant example was much 15 more brittle thansimilar films prepared with modified clay (modified bentonite) fillers,e.g., in Examples 1, II, and III. Brittleness is objectionable becauseif the film is fractured, e.g., by bending or flexing, its permeabilityis increased substantially.

EXAMPLE XVIII The general procedure of Example V was repeated. However,in this instance the clay film was not modified (i.e., the clay film wasnot treated with a solution of chromium (III) sulfate). The resultingfilm was stripped from the surface on which it was formed, thereby toform a self-supporting laminate film. The permeability of thisself-supporting laminate film to dry oxygen was less than 1 lO cc.(s.t.p.) cm./cm. sec. atm. at 35 C. but the permeability of this film tomoist oxygen (i.e., oxygen about 50-95% saturated with Water vapor atabout 35 C.) was about 1 10 cc. (s.t.p.) cm./ cm. sec. atm. at 35 C.

Permeabilities reported in the above examples, unless it is statedotherwise where permeability data are reported, were determined withmoist or humid gases (i.e., gases which were about 50-95% saturated withwater vapor at about 35 Q).

Where using platelike particles, or platelets, of at least one organiccompound as filler in the process of my invention, such compound cannotbe used with polymer systems containing solvents in which the particularplatelike organic compound is soluble, and drying of films in which suchorganic compound is present must be conducted below the melting point ofsaid platelike compound.

As used in the specification and claims of this application: (a) Theterm percent means percent by weight unless otherwise defined Whereused; (b) The term cc. means cubic centimeters; (c) The term mil means0.001 inch; (d) The term s.t.p. means standard temperature and pressure(i.e., one atmosphere and 0 C.); (c) The term atm. means atmosphere(i.e., 760 millimeters of mercury); (f) The term sec. means second; (g)The term cm. means centimeter; (h) The term cm. means square centimeter;and (i) A. means Angstrom units.

What is claimed is:

1. A process for preparing a self-supporting film having a lowpermeability to gases comprising applying at least one coating of apolymer-diluent system consisting of dispersions or solutions of afilm-forming polymer consisting essentially of a vinyl or vinylidenehomopolymer or copolymer dissolved or dispersed in water or an organicsolvent, said polymer-diluent system being filled with a mineral,inorganic, or organic material having a platelike structure, to asubstrate, and, after applying such coating;

(a) adjusting the thickness of the coating;

(b) drying the coating to a solid state, whereby a film is formed, thefilm being laminated to the substrate; and

(c) stripping the film from the substrate.

2. A process for preparing a self-supporting laminate having a lowpermeability to gases comprising applying at least one coating of apolymer-diluent system consisting of dispersions or solutions of afilm-forming polymer consisting essentially of a vinyl or vinylidenehomopolymer or copolymer dissolved or dispersed in water or an organicsolvent, said polymer-diluent system being filled with a mineral,inorganic, or organic material having a platelike structure, to asubstrate, and, after applying such coating;

(a) adjusting the thickness of the coating;

(b) drying the coating to a solid state, whereby a film is formed, thefilm being laminated to the substrate;

(c) applying at least one coating of a polymer-diluent consisting ofdispersions or solutions of a film-forming polymer consistingessentially of a vinyl or vinylidene homopolymer or copolymer dissolvedor dispersed in water or an organic solvent to the aforesaid film, and,after applying such coating;

(d) adjusting the thickness of said coating of filmformingpolymer-diluent system;

(e) drying said coating of film-forming polymer-diluent system to thesolid state, whereby a second film is formed, said second film beinglaminated to the film prepared from the filled film-formingpolymer-diluent system; and

(f) stripping the substrate from the film to which the substrate islaminated.

3. A process for preparing a self-supporting laminate having a lowpermeability to gases comprising applying at least one coating of apolymer-diluent system consisting of dispersions or solutions of afilm-forming polymer consisting essentially of a \vinyl or vinylidenehomopolymer or copolymer dissolved or dispersed in water or an organicsolvent to a substrate, and, after applying such coating;

(a) adjusting the thickness of the coating;

(b) drying the coating to a solid state, whereby a first polymer film isformed, said film being laminated to the substrate;

(c) applying a coating of a dispersion of a mineral,

inorganic, or organic filler having a platelike structure to the film;

(d) adjusting the thickness of the coating of filler;

(e) drying the coating of filler to a substantially liquid free state,whereby a layer of filler is formed on the first polymer film, saidlayer of filler being on top of and laminated to the first polymer film;

(f) applying at least one coating of a polymer-diluent system consistingof dispersions or solutions of a film-forming polymer consistingessentially of a vinyl or vinylidene homopolymer or copolymer dissolvedor dispersed in water or an organic solvent to said layer of filler,and, after applying such coat- (g) adjusting the thickness of thecoating of polymerdiluent system; and

(h) drying said coating to the solid state, whereby a second polymerfilm is formed, said second polymer film being on top of and bonded tothe layer of filler.

4.. The process of claim 3 in which the substrate is a stripped from thefilm to which the substrate is laminated.

5. The process of claim 3 in which about 05-15% based on the dry weightof the filler present, of polymeric additive selected from the groupconsisting of polyvinyl methyl ether and polyethylene oxide isincorporated into the dispersion of filler.

6. A process for preparing a self-supporting laminate having a lowpermeability to gases comprising applying at least one coating of apolymer-diluent system consist ing of dispersions or solutions of afilm-for ming polymer consisting essentially of a vinyl or vinylidenehomopolymer or copolymer dissolved or dispersed in water or an organicsolvent to a substrate, and, after applying such coating;

(a) adjusting the thickness of the coating;

(b) drying the coating to a solid state, whereby a first polymer film isformed, said film being laminated to the substrate;

(c) applying a coating of a dispersion of a purified clay-like mineralhaving a platelike structure to the first polymer film;

(d) adjusting the thickness of the coating of clay-like mineral;

(e) drying the coating of clay-like mineral to a substantially liquidfree state, whereby a layer of clayli ke mineral is formed on top ofsaid first polymer Elm, said layer being laminated to said first polymer(f) applying a coating of a solution of at least one salt of at leastone element selected from the group consisting of aluminum and atransition element 17 having an atomic number of 21-32, 39-51, or 57-83to said layer of clay-like mineral;

(g) allowing the coating of said solution to remain in contact With themineral layer for about seconds to about minutes, to modify said minerallayer;

(h) washing said solution from the modified mineral layer;

(i) drying the modified mineral layer to a substantially liquid freestate;

(j) applying at least one coating of a polymer-diluent system consistingof dispersions or solutions of a film-forming polymer consistingessentially of a vinyl or winylidene homopolymer or copolymer dissolvedor dispersed in Water or an organic solvent to the washed and driedmodified mineral layer, and, after applying such coating;

( k) adjusting the thickness of said coating of film formingpolymer-diluent system; and

(l) drying said coating of film-forming polymer-diluent system to asolid state, whereby a second polymer film is formed, said secondpolymer film being on top of and laminated to the layer of modifiedclay-like mineral.

7. The process of claim 6 in which the substrate is stripped from thefilm to which the substrate is laminated.

8. The process of claim 6 in which about 0.5l5%, based on the dry weightof the purified clay-like mineral present, of a polymeric additiveselected from the group consisting of polyvinyl methyl ether andpolyethylene oxide is incorporated into the dispersion of clay-likemineral.

9. A process for preparing a self-supporting laminate having a loWpermeability to gases comprising applying at least one coating of apolymer-diluent system consisting of dispersions or solutions of afilm-forming polymer consisting essentially of a vinyl or vinylidenehomopolymer or copolymer dissolved or dispersed in water or an organicsolvent to a substrate, and, after applying such coating;

(a) adjusting the thickness of the coating;

(b) drying the coating to a solid state, whereby a first polymer film isformed, said film being laminated to the substrate;

(c) applying at least one coating of a polymer-diluent system consistingof dispersions or solution of a filmforming polymer consistingessentially of a vinyl or Vinylidene homopolymer or copolymer dissolvedor dispersed in water or an organic solvent, said polymer-diluent systembeing filled with a mineral, inorganic, or organic material having aplatelike structure, to said first polymer film, and, after applyingsuch coating;

(d) adjusting the thickness of the coating of filled polymer-diluentsystem;

(e) drying the coating of filled polymer-diluent system to the solidstate, whereby a film of filled polymer is formed, said filled polymerfilm being on top of and laminated to the aforesaid first polymer film;

(f) applying at least one coating of a polymer-diluent system consistingof dispersions or solutions of a filmforming polymer consistingessentially of a vinyl or vinylidene homopolymer or copolymer dissolvedor dispersed in Water or an organic solvent to the film of filledpolymer, and, after applying such coating;

(g) adjusting the thickness of the coating of film-formingpolymer-diluent system; and

(h) drying the coating of polymer-diluent system to a solid state,whereby a second polymer film is formed, said second polymer film beingon top of and laminated to the film of filled polymer.

10. The process of claim 9 in which the substrate is stripped from thefilm to which said substrate is laminated.

References Cited UNITED STATES PATENTS 3,085,731 4/1963 Wilkins ll776(P)X 3,142,583 7/1964 McMahon 117-62 3,230,289 l/1966 Eder et a1. 2642l63,428,483 2/1969 Owens 1l7138.8(A) 3,498,827 3/1970 Vanderbilt et a1117-75 WILLIAM D. MARTIN, Primary Examiner R. HUSACK, Assistant ExaminerUS. Cl. X.R.

